Small plug-type surge protector

ABSTRACT

A small, efficient and inexpensive surge protector to protect delicate, transistorized equipment such as TV sets and the like. The surge protector comprises a plug incorporating one or more fuses and a firing device including a circuit having a Siemens tube, or other non-polarized gas filled tube. The surge protector is plugged into a wall outlet and the line cord from the device to be protected is plugged into the female contacts at the opposite end of the protector. When a voltage surge enters the protector, it passes through the fuses and activates the gas filled firing device, causing a near short circuit across the female contacts, protecting the load and melting one or both of the fuse elements. A neon indicator is utilized so that it is always readily apparent whether or not the surge protector is in operative condition.

United States Patent [191 Brown 1 SMALL PLUG-TYPE SURGE PROTECTOR [76]Inventor: Dwight L. Brown, PO. Box 439,

Barbourville, Ky. 40906 [22] Filed: July 2, 1973 [21] Appl. N0.: 375,491

[52] US. Cl.... 317/16, 317/9 A, 317/50, 317/62 [51] Int. Cl. H02h 9/04,H02h 9/06 [58] Field of Search 317/16, 40 A, 48, 50, 51, 3l7/61.5, 61,68; 337/198, 201, 206, 269, 263, 266, 268, 270; 339/147 P, 256 SP, 258

[111 3,840,781 [451 Oct. 8, 1974 5/1972 Grenier ..317/16 3/1973 Brown..3l7/16 [5 7] ABSTRACT A small, efficient and inexpensive surgeprotector to protect delicate, transistorized equipment such as TV setsand the like. The surge protector comprises a'plug incorporating one ormore fuses and a firing device including a circuit having a Siemenstube, or other non-polarized gas filled tube. The surge protector isplugged into a wall outlet and the line cord from the device to beprotected is plugged into the female contacts at the opposite end of theprotector. When a voltage surge enters the protector, it passes throughthe fuses and activates the gas filled firing device, causing a nearshort circuit across the female contacts, protecting the load andmelting one or both of the fuse elements. A neon indicator is utilizedso that it is always readily apparent whether or not the surge protectoris in operative condition.

12 Claims, 9 Drawing Figures l SMALL PLUG-TYPE SURGE PROTECTOR CROSSREFERENCE TO RELATED APPLICATION This application, although neither acontinuation-inpart application nor a divisional application, is closelyrelated to application Ser. No. 335,021 in the name of the same inventorand filed Feb. 23, 1973; this latter application is acontinuation-in-part of an earlier filed application in the name of thesame inventor filed Jan. 3, 1972, and bearingSer. No. 215,060, nowUnited States Patent No. 3,723,820.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention hasparticular application in the protection of transistorized equipmentfound in homes, office buildings and the like wherein it is notimportant that the protector reset itself after having once performedits protecting function. Transistors are usually operated somewhere neartheir maximum voltage rating and, therefore, it is necessary that asurge device fire on spikes slightly higher than the normal linevoltage. The peak voltage across a 120 volt line is approximately 168volts so the plug protector should incorporate a firing device thatoperates at about 200 volts. The device is arranged to shunt a surgeeven though there is no current through the fuses. This permits a pieceof equipment to be turned off and still protected, an important featurein view of the fact that many times TV sets, for example, are damaged byvoltage spikes even though theyare turned off.

The plug-type surge protector of this invention may beused to protectcolor TV sets, CATV equipment using transistors, heavier equipment suchas room air conditioners, and similar items. The equipment to beprotected will determine the amperage of the fuses incorporated into theplug along with the non-polarized gas filled firing tube device. lfacolor TV set, for example, is to be protected, fuses of the five ampere,fast blow type would be used; if heavier equipment such as a room airconditioner is to be protected, fuses with a higher amperage ratingwould be necessary because of the heavier current involved.

2. Description of the Prior Art A rather extensive patentability andvalidity search was conducted on this plug-type surge protector. Some 45patents were developed. Additionally, other patents of some interest areof record in thesaid application and said patent earlier mentioned.Although the purpose of the search was to develop the most pertinentprior art to the invention disclosed and claimed herein, no assertion ismade that the best art was actually found. It is believed that thefollowing patents are the more pertinent: 1,942,178, Machenheimer;2,244,044, Bishop; 2,404,407, Seurynik; 2,742,545, Sundt; 2,786,112,Pempey; 2,910,625, Carpenter; 3,047,695, Borys; 3,184,569, McLaren;3,187,224, Le Massena; 3,323,017, Powell et a1; 3,368,110, Taylor,3,369,153, Arnold et a1; 3,386,004, Dwyer; 3,452,252, Mapham; 3,659,252,Brown; and 3,660,719 Grenier.

Patent Nos. 3,368,110 and 3,660,719 appear to be the closest, althoughothers of the patents do disclose various forms of fused plugs.

With reference to Patent No. 3,368,] Taylor, it is known that voltagesurges sometimes reach 2,600 volts across a 120 volt power line. It isnecessary, therefore,

for a surge protective device to be able to withstand such high voltagespikes and have sufficient current carrying capacity to melt theprotective fuse elements placed ahead of the 1ring" device. In order toprotect a device which draws only a nominal current, such as a color TVset, Taylors safety adapter would need diodes capable of withstanding3,000 volts and a 1 cycle current of approximately 5 amperes. Diodes ofthis type are rather expensive. Furthermore, diodes will not react to asurge as fast as the non-polarized gas filled tubes incorporated in theinstant plug-type surge protector. It does not appear that the Taylorsafety adapter could be an effective surge protector capable ofprotecting delicate, transistorized equipment and it would be expensiveto manufacture.

The device of Grenier, 3,660,719, is evidently designed to protectequipment less sensitive to voltage surges than transistorized CATV andTV equipment. This patent discloses the use of a ballast resistor inseries with a gas filled, spark gap device. It evidently counts on beingable to reset itself because no fuse is employed and the ballast is usedto quench the arc across the gas filled device. The ballast resistor isin series in the firing circuit and will slow down the firing time ofthe circuit to the extent that a damaging pulse could pass on by theshunting device.

SUMMARY OF THE INVENTION The small plug-type surge protector comprises abody housing tubular fuses, fuse holders, male contacts, a gas filledfiring device, a neon indicator light, and a female electrical contact.This latter contact is itself a fuse holder, a female electricalcontact, a Siemens tube holder, a neon pilot light connector and a meansfor positioning it within the housing.

The male elements at one end of the plug surge protector are pluggedinto a wall outlet and the line cord from the device to be protected isplugged into the female contacts at the opposite end of the protector.The various members are so arranged that current normally passes throughthe fuses to the device to be protected. The non-polarized gas filledfiring tube is placed directly across the line, between the device to beprotected and the fuses, with nothing to delay the firing time exceptthe tube itself. The time lag in the thermal fuses has nothing to dowith the speed with which the surge is shunted; but rather the speed isdependent solely upon the speed with which the gas filled device fires.

The neon pilot light indicates the condition of the surge protector. Ifthe light is on, the fuses are intact and the device is operable. Whenthe device fires on a surge, one or both of the fuses are blown. Theplug is such that these fuses are readily replaceable by pushing themout through appropriate holes at the male end of the device. If the gasfilled tube is damaged, the replaced fuses will blow, indicating thisfact. A firing device, however, can itself be easily replaced by liftingout the old one and pushing a new one into the place provided. Thefemale contact clip is reversible so that only one type need be made.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective viewshowing the plug-type surge protector.

FIG. 2 is a plan view of the interior of one-half of the plug assembly.

FIG. 3 is a plan view of the other half of the plug assembly.

FIG. 4 is a top plan view of the plug when assembled.

FIG. 5 is a bottom plan view of the plug when assembled.

FIG. 6 is a perspective view of the all-purpose female electricalcontact.

FIG. 7 is a diagrammatic view of a circuit which may be incorporated inthe plug-type surge protector.

FIG. 8 is a diagrammatic view of another circuit which may beincorporated in the protector.

FIG. 9 is a schematic view of a modification of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 through 5the small plug-type surge protector is comprised of a pair of housingmembers and 21. The various members included within the protector areshown as located within member 21 while member 20 is provided withsuitable cavities to accommodate such members. It will be apparent thatit would be possible to reverse these members.

As a matter of fact these members 20 and 21, before the insertion of theworking elements, are identical.

Noting that throughout the description of this invention like numeralswill be used to identify like parts, each. of the male contacts 22comprises a pair of elongated strips 22a and 22b, joined at their outerends as at 22c, and having a bulge 22d to insure good electricalconnection when the members 22 are inserted within the usual wall outletfound in homes, office buildings and the like. Extending from that endof the member 22 located within the plug is a clip' extension 23 adaptedto receive and have electrical contact with a tubular fuse 24. The fuse24 has caps 25 and 26 adjacent its ends and connected between these capsis the fuse element 27. When the fuse 24 is in the position shown inFIG. 3, the cap 25 will be in electrical contact with the extension 23of the male element 22. The members22 and 23 may be separate elementssuitably welded or otherwise held together in electrical contact or themember 23 may be integral with one of the members 22a or 22b; otherarrangements may readily occur to those skilled in the art.

A pair of female contacts generally indicated at 28 is incorporated inthat end of the plug which is opposite that in which the male elements22 are located. These female contacts are shown in FIG. 3 and one ofthem is shown in perspective in FIG. 6. The female contact 28 isreversable so that only one type need be made. The female member 28comprisesa body strip 29 having a female contact member 30, a fuseholding clip 31, a pilot light connector 32, a Siemens tube holder 33,and shoulders 34 for positioning it within the housing 21.

The extended portions 33 of the female contact 28 serve to makeelectrical contact with the Siemens tube 35 and to clamp it in positionwithin the housing members 20, 21. A neon pilot light 36 is connectedacross the members 33. Preferably a suitable resistance 37 isincorporated in the circuit which includes the pilot light 36.Reflectors 38 and 39 are provided in the members 20 and 21 so that thepresence of the pilot light 36 may be observed from either side of theplug.

In use the plug will be plugged into the usual wall outlet by means ofthe male elements 22a, 22b the ends of which may be joined as at 220,see FIG. 4. The device to be protected is then plugged into the surgeprotector, the prongs of the plug which is connected to the device beinginserted through the openings 40 so as to contact the female electricalcontacts 30. The surge protector, at the end adjacent the femalecontacts, is provided with small openings 41 through which a suitableinstrument may be passed in order to push a spent fuse 24 out of theprotector, that end of the protector adjacent the male elements 22 beingprovided with openings 42 through which such fuse may pass. A new fusemay then be inserted through such opening 42 into the clip elements 23and 31 which are in electrical contact with the male prongs 22 andfemale connectors 30 respectively. Circuit elements 43 connect the pilotlight 36 across the extended portions 33 of the female contact member28, 30 and are hooked onto the ears 32 provided in such portions 33.

In FIG. 7 the basic wiring diagram of the surge protector isdiagrammatically illustrated, the various reference numerals of theelectrical contacts described in connection with the protector of FIG. 3being used to designate the corresponding parts in FIG. 7. Thus, currentfrom the wall outlet will pass through the male contacts 22, through thefuses 24, through the female contact elements 33 and the gas filled tube35, and through the female connector portions 30, the pilot light 36 andits resistor 37 being connected across this circuit by the conductors43.

It is conceivable that the surge protector of FIGS. 1 through 7 could bemodified as diagrammatically illustrated in FIG. 8 by incorporatingtherein a suitable choke 44 and an additional resistor 45 for theSiemens tube 35. This in effect would result in a circuit arrangementfor the surge protector like that claimed and disclosed in the saidclosely related application. The use of the choke 44 promotes the fastfiring of the tube 35.

A further modification of the invention is diagrammatically illustratedin FIG. 9 wherein like reference numerals have been employed torepresent parts and elements like those described in connection with theembodiments of FIGS. 1 through 7 and FIG. 8. In this modification areceptacle 47 into which the load may be plugged is connected by anextension cord 46 to the female elements 30 of the surge protector 20,21. The Siemens tube, or other non-polarized gas filled tube, is againindicated at 35 but in this modification it is incorporated within thereceptacle 47. Electrically the setup of FIG. 9 is the equivalent ofthat of FIGS. 3 and 7. The firing device 35 has simply been moved fromthe plug 20, 21 to the receptacle 47. The plug 48 from the load to beprotected is plugged into the receptacle 47 rather than directly intothe surge protector 20, 21.

The various elements of which the surge protector is comprised have beenshown as incorporated in plug member 21 in FIG. 1. Plug member 20,therefore, will be provided with corresponding cavities to receive thesevarious elements. Thus, as shown in FIG. 2, the member 20 will havecavities 49 to receive the fuses 24, a cavity 50 to receive the Siemenstube 35, cavities 51 for the male prongs 22, and a cavity 52 to receivethe reflector 38. The member 21 has corresponding cavities. The member'is also provided with openings 42 through which the fuses 24 may passand with the punch holes 41 by means of which the fuses may be ejectedthrough the openings 42. The halves 20 and 21 of the surge protector maybe joined by suitable fasteners 53 as best seen in FIG. 1. As earlierindicated, these halves 20 and 21 may be molded identical to one anotherand the remaining elements then placed in either half whereafter thehalves are joined.

The use of the Siemens tube 35, or other nonpolarized gas filled tube,is important to the operability of the surge protector for the reasonthat fuses are not fast enough to protect delicate equipment.Furthermore, fuses, or other similar thermal devices, will not alwaysgive good protection against voltage surges, they not being fast enoughfor this purpose, although they usually will provide adequate protectionagainst increases in current. The surge protector of this invention isessentially a voltage device,,not a current device.

Referring again to FIG. 7, two fuses 24 are used to protect the inputcircuit. This is especially useful in a non-polarized circuit (a circuitin which the line-of highest or lowest potential isnt known) such as anA.C. circuit which is known as a floating ground. The Siemens tube beingnonpolarized will fire in either direction so it doesnt matter which wayit is plugged into the outlet. This isconsidered better than using athreeprong plug and socket because it is possible for the three-wireoutlets to be improperly wired. The device shown in FIGS. 3 and 7'willfire on a surge regardless of polarity in the wiringcircuit. Whenever asurge comes over the power line, it passes through the fuses and then isshunted to ground or the line of lowest potential, at which time theSiemens tube is virtually short circuited and the excessive currentblows one or both of the fuses. The neon pilot light 36, with itsassociated resistor 37, is used to indicate that the device is inoperable condition; if a fuse is blown, the pilot light wont burn.

The plug-type surge protector of this invention is indeed small andcompact. In practice it has been incorporated in a plug which is 1 /2in. wide, 1% in. long and /8 in. thick. It is relatively inexpensive andeasily and quickly assembled through the use of only a pair of pliersand a screwdriver. It has been used to protect TV sets and some CATVequipment using transistors.

None of the equipment connected to this surge protector has been damagedalthough like equipment operating nearby without surge protection hasbeen badly damaged. The combination of, and arrangement of, the variousparts and elements to make a small, efficient and inexpensive surgeprotector to protect delicate,

transistorized equipment is an important part of this invention.

The use of the Siemens tube or other non-polarized gas filled tube isconsidered important. Laboratory tests have shown that these gas filleddevices will fire within two nanoseconds from the time the pulse isapplied. Such speed would allow an electrical pulse to travel a distanceof less than two feet during the transition time. thuspreventing a pulseof any consequence from reaching a protected device. Another feature ofthese gas filled tubes is that, although they are small in size, theywill withstand a peak discharge current of amperes for one one-hundredthof a second, 500 amperes for one millisecond and 5000 amperes for onemicrosecond. Another desirable feature is that they normally deterioratein the fail-safe direction.

A further important feature of this invention is the construction of thefemale contact generally indicated at 28 and best seen in FIG. 6. Themultiple purposes served by this contact in part at least makes possiblea surge protector resulting in such a small, convenient package.

It is believed that the foregoing description is complete. It will beapparent to those skilled in the art, however, that modifications may bemade therein without departing from the scope and spirit thereof. lt isto be understood that while the invention has been described in terms ofparticularelements and structures, such are not to constitute alimitation on the invention except insofar as they are specifically setforth in the subjoined claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A small plug-type surge protector adapted for easy assembly andrepair comprising:

a. a housing;

b. first and second male contacts mounted in said housing in parallelspaced relationship, with the ends thereof extending through first andsecond perforations in a first end of said housing and adapted to beplugged into a wall outlet;

0. first and second female contacts mounted in said housing in parallelspaced relationship and in alignment with a pair of first and secondperforations in a second end of said housing;

d. said first male contact and said first female contact each having aspring clipadapted to receive and frictionally engage a firsttubular-type fuse;

e. said spring clips being so configured that said first fuse may beaxially shifted into and out of engagement therewith through a thirdperforation in said first housing end;

f. means electrically connecting said second male and female contacts;

g. each of said female contacts having, in electrical contact therewith,a laterally extending spring arm, said spring arms extending toward eachother; and

h. a firing device comprising a non-polarized gas filled tubefrictionally engagedbetween and in electrical contact with said springarms; whereby, when said surge protector is plugged into a wall outletand when a load to be protected from voltage surges is plugged into saidfemale contacts of said surge protector, a voltage surge will cause saidfiring device to fire and blow said first fuse before said surge reachessaid load.

2. The surge protector of claim 1 including a pilot light connectedacross said female contacts, whereby said pilot light is on wheneversaid male contacts are engaged within a wall outlet and said fuse is inoperative condition.

3. The surge protector of claim 2 including a resistor in series withsaid pilot light.

4. The surge protector of claim 2 in which each of said female contactshas a connecting means to which said pilot light is connected.

5. The surge protector of claim 1 in which a. said second male contactand said second female contacteach have a spring clip adapted to receiveand frictionally engage a second tubular-type fuse;

b. said spring clips being so configured that said second fuse may beaxially shifted into and out of engagement therewith through a fourthperforation in said first housing end; and

c. said means electrically connecting said second male and femalecontacts comprising said second tubular fuse.

6. The surge protector of claim including a pilot light and a resistorfor said pilot light connected across said female elements so that saidpilot light is on whenever said male contacts are engaged within a walloutlet and said fuses are in operative condition.

7. The surge protector of claim 6 in which said housing is comprised ofa pair of identical halves, each half having cavities to receive saidmale contacts, said female contacts, said spring clips, said fuses, saidfiring device, said pilot light and said resistor; and means to holdsaid halves together.

8; The surge protector of claim 1 in which said housing is comprised oftwo identical halves, each half having cavities to receive said malecontacts, said female contacts, said fuse, and said firing device.

9. The surge protector of claim 1 in which said firing device is aSiemens tube.

10. An element for use in a surge protector of the type set forth inclaim 1, said element comprising a body to be received in a suitablehousing, a female contact extending from said body, a spring clipextending from said body and adapted to slidably receive a fuse, anextension on said body adapted to engage a firing device, and aconnecting means on said extension for engaging a pilot light lead.

11. The surge protector of claim 1 in which said first fuse may beaxially shifted out of engagement with said spring clips through saidthird perforation in said first housing end by' passing an instrumentthrough a third perforation in said second housing end so as to pushsaid first fuse through said first perforation in said first housingend, said third perforation in said second housing end being in axialalignment with said third perforation in said first housing end.

12. The surge protector of claim 5 including third and fourthperforations in said second housing end coaxially aligned with saidthird and fourth perforations in said first housing end whereby saidfirst fuse may be shifted out of engagement with its spring clips andthrough said third perforation in said first housing end by insertion ofanelongated tool into said third perforation in said second housing endand similarly said second fuse may be shifted out of engagement with itsspring clips and through said fourth perforation in said first housingend by insertion of said tool in said fourth perforation in said secondhousing end.

1. A small plug-type surge protector adapted for easy assembly andrepair comprising: a. a housing; b. first and second male contactsmounted in said housing in parallel spaced relationship, with the endstheReof extending through first and second perforations in a first endof said housing and adapted to be plugged into a wall outlet; c. firstand second female contacts mounted in said housing in parallel spacedrelationship and in alignment with a pair of first and secondperforations in a second end of said housing; d. said first male contactand said first female contact each having a spring clip adapted toreceive and frictionally engage a first tubular-type fuse; e. saidspring clips being so configured that said first fuse may be axiallyshifted into and out of engagement therewith through a third perforationin said first housing end; f. means electrically connecting said secondmale and female contacts; g. each of said female contacts having, inelectrical contact therewith, a laterally extending spring arm, saidspring arms extending toward each other; and h. a firing devicecomprising a non-polarized gas filled tube frictionally engaged betweenand in electrical contact with said spring arms; whereby, when saidsurge protector is plugged into a wall outlet and when a load to beprotected from voltage surges is plugged into said female contacts ofsaid surge protector, a voltage surge will cause said firing device tofire and blow said first fuse before said surge reaches said load. 2.The surge protector of claim 1 including a pilot light connected acrosssaid female contacts, whereby said pilot light is on whenever said malecontacts are engaged within a wall outlet and said fuse is in operativecondition.
 3. The surge protector of claim 2 including a resistor inseries with said pilot light.
 4. The surge protector of claim 2 in whicheach of said female contacts has a connecting means to which said pilotlight is connected.
 5. The surge protector of claim 1 in which a. saidsecond male contact and said second female contact each have a springclip adapted to receive and frictionally engage a second tubular-typefuse; b. said spring clips being so configured that said second fuse maybe axially shifted into and out of engagement therewith through a fourthperforation in said first housing end; and c. said means electricallyconnecting said second male and female contacts comprising said secondtubular fuse.
 6. The surge protector of claim 5 including a pilot lightand a resistor for said pilot light connected across said femaleelements so that said pilot light is on whenever said male contacts areengaged within a wall outlet and said fuses are in operative condition.7. The surge protector of claim 6 in which said housing is comprised ofa pair of identical halves, each half having cavities to receive saidmale contacts, said female contacts, said spring clips, said fuses, saidfiring device, said pilot light and said resistor; and means to holdsaid halves together.
 8. The surge protector of claim 1 in which saidhousing is comprised of two identical halves, each half having cavitiesto receive said male contacts, said female contacts, said fuse, and saidfiring device.
 9. The surge protector of claim 1 in which said firingdevice is a Siemens tube.
 10. An element for use in a surge protector ofthe type set forth in claim 1, said element comprising a body to bereceived in a suitable housing, a female contact extending from saidbody, a spring clip extending from said body and adapted to slidablyreceive a fuse, an extension on said body adapted to engage a firingdevice, and a connecting means on said extension for engaging a pilotlight lead.
 11. The surge protector of claim 1 in which said first fusemay be axially shifted out of engagement with said spring clips throughsaid third perforation in said first housing end by passing aninstrument through a third perforation in said second housing end so asto push said first fuse through said first perforation in said firsthousing end, said third perforation in said second housing end being inaxiAl alignment with said third perforation in said first housing end.12. The surge protector of claim 5 including third and fourthperforations in said second housing end coaxially aligned with saidthird and fourth perforations in said first housing end whereby saidfirst fuse may be shifted out of engagement with its spring clips andthrough said third perforation in said first housing end by insertion ofan elongated tool into said third perforation in said second housing endand similarly said second fuse may be shifted out of engagement with itsspring clips and through said fourth perforation in said first housingend by insertion of said tool in said fourth perforation in said secondhousing end.